The present invention provides a method and a system for automatic keyword extraction based on supervised or unsupervised machine learning techniques. Novel linguistically-motivated machine learning features are introduced, including discourse comprehension features based on construction integration theory, numeric features making use of syntactic part-of-speech patterns, and probabilistic features based on analysis of online encyclopedia annotations. The improved keyword extraction methods are combined with word sense disambiguation into a system for automatically generating annotations to enrich text with links to encyclopedic knowledge.